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India lowers its 2011 monsoon forecast

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India’s meteorological department has issued its second long range forecast for the 2011 monsoon and has lowered its estimate. Rainfall will be 95% of the 50-year average in the June-September season, which are the monsoon months. In April, the Indian Meteorological Department predicted a monsoon that would be 98% of the long-term average. Normal precipitation is considered to be 96%-104% percent of the long-term average.

India’s agriculture-dependent population has been hoping for adequate rainfall to harvest good quantities of foodgrain and lentils for a second year and bring down inflation, which has led the Reserve Bank of India – the central bank – to raise rates for a 10th time in 15 months. Agriculture accounts for 14% of the economy and a reduced harvest can further lower rural incomes and send food inflation higher than it already is. Inflation in India is the highest among Asia’s major economies.

Bloomberg reported that the wholesale price index in India accelerated 9.06% in May after having increased 8.66% a month earlier, according to official data released on June 14. An index measuring wholesale prices of farm products including milk and lentils rose 8.96% in the week ended June 4 from a year earlier, according to the commerce ministry. India imported record quantities of sugar, lentils and oilseeds in 2009 following the weakest monsoon that year since 1972.

The IMD’s ‘long period’ is 1951-2000 and the department considers probabilities for the country (all-India) and four major regions: north-west India, central India, north-east India and south peninsula. “Over the four broad geographical regions of the country, rainfall for the 2011 Southwest Monsoon Season is likely to be 97% of its LPA over North-West India, 95% of its LPA over North-East India, 95% of its LPA over Central India and 94% of its LPA over South Peninsula, all with a model error of ± 8 %.”

The IMD also employs a six-parameter statistical forecasting system to prepare probability forecasts for five pre-defined rainfall categories. These are deficient (less than 90% of LPA), below normal (90-96% of LPA), normal (96-104% of LPA), above normal (104-110% of LPA) and excess (above 110% of LPA). The forecasted probabilities for the 2011 southwest monsoon season based on this system in percentage for the above 5 categories are 19%, 37%, 37%, 6% and 1%

The department’s ‘Summary of the Update Forecasts for 2011 Southwest Monsoon Rainfall’ has said:

(1) Rainfall over the country as a whole for the 2011 southwest monsoon season (June to September) is most likely to be below normal (90-96% of LPA). Quantitatively, monsoon season rainfall for the country as a whole is likely to be 95% of the long period average with a model error of ±4%. The Long period average rainfall over the country as a whole for the period 1951-2000 is 89 cm.

(2) Rainfall over the country as a whole in the month of July 2011 is likely to be 93% of its LPA and that in the month of August is likely to be 94% of LPA both with a model error of ± 9 %.

(3) Over the four broad geographical regions of the country, rainfall for the 2011 Southwest Monsoon Season is likely to be 97% of its LPA over North-West India, 95% of its LPA over North-East India, 95% of its LPA over Central India and 94% of its LPA over South Peninsula, all with a model error of ± 8 %.

According to Reuters, government officials played down concerns that lower rainfall could fan inflation and dampen growth. “There is no need to press the panic button, as June rains are still above normal,” said Shailesh Nayak, the top civil servant in the ministry of earth sciences which controls the country’s weather office.

While rains could be slightly lower than normal in July, India’s chief forecaster said distribution was key. “There are chances the monsoon will pick up after July 15 once it covers the entire country,” said D. Sivananda Pai, director at the state-run National Climate Center. “Don’t go by the numbers, it is the distribution (of the rains) which we are still hoping to be good.” The weather office predicted 27 centimetres of rain in July compared with long-term average rainfall of 29 centimetres, and rains at 24 centimetres in August, when seeds start maturing, compared with long-term averages of 26 centimetres.

Weather office chief Ajit Tyagi remained optimistic. “Ninety five percent is a good forecast,” Tyagi said. “Had it been 90% of the long-term average then it would have been a cause for concern,” he said, adding that in the past slightly below normal monsoon rains had also seen adequate farm output because they were well distributed in the major crop growing regions.

Explaining climatic conditions over the equatorial Pacific and Indian Oceans, the department’s second long range said moderate to strong La Nina conditions that prevailed in the equatorial Pacific during mid-August 2010 to early February 2011 weakened during subsequent months and dissipated to neutral conditions around mid-May 2011. The latest forecasts from a majority of the dynamical and statistical models indicate strong probability for the present ENSO-neutral conditions to continue during the current monsoon season and the remaining part of 2011.

It is important to note that in addition to El Niño and La Niña events, other factors such as the Indian Ocean Sea surface temperatures (SSTs) have also significant influence on India monsoon. However, the latest forecasts do not suggest development of either a positive or a negative Indian Ocean Dipole event during the 2011 monsoon season. In the absence of strong monsoon forcing from both Pacific and Indian Oceans, intraseasonal variation may become more crucial during this southwest monsoon season and lead to increased uncertainty in the monsoon forecasts.